The invention relates to a method for biotechnologically producing valuable products, in which method a medium is fed to a bioreactor and subjected to a fermentation process, and in which method the valuable product is harvested, as filtered permeate and/or as concentrated retentate, by way of a downstream cross-flow filtration unit, and residues are supplied again to the bioreactor until harvesting as retentate.
The invention furthermore relates to a device for biotechnologically producing valuable products, which device essentially comprises a bioreactor having an upstream first feed receptacle for a medium and a downstream cross-flow filtration unit whose permeate line is connected to a first harvest receptacle and whose retentate line leads back into the bioreactor.
EP 0 307 737 B1, for example, discloses a method for biotechnically producing valuable products. However, particularly as far as producing recombinant proteins is concerned, a contradiction arises between the requirement for a cell productivity which is as high as possible (high cell density culture) and the requirement for the membranes (cross-flow membranes) of cross-flow microfiltration units to have a long service life. In particular, increasing the permeate flux above a particular limit value at a given biomass concentration in the product solution can lead to a dramatic increase in the transmembrane pressure and, as a result, to the membrane pores becoming blocked, i.e. to the membrane becoming fouled.